Campanula is a large genus that encompasses many varieties of plants. Also called bellflowers, most varieties of campanula are easy to grow from plant divisions or seeds. Some campanulas are considered hardy perennials, some are hardy biennials, and some that grow in the warm southern climate are hardy annuals. Small campanulas are commonly used in rock gardens or as border plants or potted plants. Campanulas create season-long displays of flowers. They are stunning in mass plantings, and also when used for naturalizing.
Campanulas are native North American wildflowers. Because they grow easily in almost any area, they have become popular garden flowers. Different varieties are known by common names including harebell, Canterbury bells, fairies' thimbles and cup and saucer.
Native campanula varieties grow throughout most of North America. They grow from Florida all the way to Alaska, throughout Canada, and they even grow in Greenland. The USDA distribution charts show only five states where campanula are not found: Hawaii, Oklahoma, Arkansas, Louisiana and Mississippi.
Campanula flowers all share similar characteristics. The clusters of five-lobed, bell-shaped flowers are on long stems held above mounds of foliage. Most flowers are shades of blue, but they can also be white or even pink. Campanulas have a long bloom period that begins in mid to late June and extends into September. Campanula flowers produce a small fruit that matures into a capsule. It contains tiny seeds that are dispersed through pores in the sides of the capsule. Rabbits and deer generally do not eat campanulas.
If you are growing campanula plants from seeds, start them indoors 10 weeks before the transplanting date. Sow the seeds thinly and barely cover them with light soil. Seeds germinate in two to three weeks. Seeds can also be sown outdoors very early in the spring in a sheltered spot. Garden centers and nurseries sell campanula plants, which will get off to a quick start in the garden.
Campanulas need full sun. Most varieties need to be watered frequently, but they like soil that dries out rapidly. Although the optimum pH level is neutral to slightly alkaline, campanulas will tolerate pH variations. Use a balanced organic fertilizer every two weeks, or add a light layer of compost.
If you remove the spent flowers regularly, or deadhead, campanulas will keep blooming until frost. Flower production stops if the plants are not deadheaded, so it is important to keep up with it. Established plantings should be divided every two to four years to keep campanulas vigorously growing. Divisions can be made in spring or fall.